1. Field of the Invention
This invention relates to a method for maintenance of an image forming device such as an electrophotographic device, etc. particularly to a method for maintenance of the image forming ability of an image forming member.
2. Description of the Prior Art
An image forming device, for example, an electrophotographic copying device is a device which repeats the steps of charging, light-exosure, development, transfer, and cleaning with the use of a photosensitive drum coated with a photoconductive material such as Se, CdS, OPC, amorphous silicon, etc. to obtain copies of an original manuscript. In such a copying device, the step of charging a photosensitive member for image formation is generally practiced by imparting charges according to corona discharge, whereby various molecular species in the air are ionized at the same time by discharging and adsorbed onto the photosensitive member. Accordingly, when a copying machine is used over a long term, the ion species on the photosensitive member are bound with moistures in the air to form an ionic film on the photosensitive member. Such films are ionic in nature and therefore the surface electric resistance at the portion on which the film is formed is lowered, whereby simultaneously with exposure after charging, charges are escaped from the portion lowered in resistance. That is, at the portion along the film, no latent image potential sufficient for development can be retained to generate the phenomenon of the so called image smearing. This image smearing will frequently occur under highly humid environment, because the moisture in the air greatly participates therein.
In the prior art, as a countermeasure against the image smearing, there have been known the method in which the drum-shaped surface of a photosensitive member is polished with a polishing material, and the method in which fine powders of cerium oxide, etc. are added into a developer and polishing is performed with a cleaning blade. However, according to any of these methods, the ionic film is removed physically by polishing together with a photoconductive material, whereby the life of the photosensitive material is markedly lowered. Also, in the method incorporating cerium oxide in a developer, lowering of fixing as well as developing characteristics cannot be avoided. Further, when the photosensitive is made of a very hard material such as amorphous silicon, it is difficult to remove by polishing an ionic material from the surface of the drum-shaped a photosensitive member, and these methods were not effective.